Need to reset Hameg HM5014-2

[teddychn]

I have a HM5014-2 and it's rotary encoder seems doesn't work. The screen looked
very dard. I'd press some combination keys and power on at the same time. In that
way could restore the settings back to factory default and the screen brightnees
behaves normally. But today, I bumped up the same issue again and forget the keys I'd
pressed before.

Does any one know the trick to reset this spectrum analyzer. I can't find the answer in
either user's manul or service manual.

Thanks!